Shock mounting



Aug. 4, 1953 R. F. NoRRls ETAL SHOCK MOUNTING Filed Oct. 26, 1944 @We/whoa @www RALPH F. NORRS ROBERT D. AVERY @3M /l Patented Aug. 4, 1953 SHOCK MOUNTING Ralph F. Norris, Madison, Wis., and Robert D. Avery, Mineola, N. Y., assignors to the United States of America as represented by the Secretary of the Navy Application October 26, 1944, Serial No. 560,450

Claims. 1

`more particularly to a shock mounting having satisfactory vibration isolation characteristics in a plurality of directions.

When relatively delicate measuring instruments are mounted in carriers such as aircraft, means must be provided for eliminating the destructive eiiects of vibration produced in the operation of the carrier. Vibration control or isolation in 'this and in other applications requires the use of a shock mounting which is soft in the direction of the disturbing forces producing vibration and which is capable of supporting the instrument to be isolated.

It is well known that the best protection against vibration is afforded by rubber shock mountings so arranged that the rubber is loaded in shear, rubber so loaded providing both softness and low damping in the direction of loading. In directions other than the direction in which the mount is loaded in shear, vibration isolation is in general unsatisfactory due to the fact that in such directions the rubber is loaded either in compression or in tension. Such shock mountings, therefore, provide for isolation of disturbing forces in a single direction. In many cases, however, disturbing forces may occur in a plurality of `directions and their directional distribution may be almost random. Consequently, adequate Vibration isolation using previous shock mountings is often diicult.

It is an object of the present invention, therefore, to provide a shock mounting in which the advantages of shear-loaded rubber are realized for isolation o1 vibrations due to simultaneous disturbing forces in a plurality of directions,

Accordingly, the invention provides, in one aspect, a rubber shock mounting comprising a beam having a mounting point substantially at the center thereof, and a pair of members extending outwardly from the beam and spaced on opposite sides of the center thereof, each of these members having a mounting point positioned adjacent its outer end.

The above and other features of the invention Will be described in the following detailed specification and pointed out in the appended claims, in which:

Fig. 1 is a schematic vieW illustrating the principle of operation of the shock mounting of the invention;

Fig. 2 is a perspective View of a shock mounting according to the invention; and

Fig. 3 is a representation of a set of orthogonal reference axes in respect to which the action of Z the shock mountings of Figs. l and 2 `may be described.

Referring to Fig. l, the shock mounting is shown as comprising a beam Ill having substantially at its center ya mounting point I2, this mounting point being shown as a hole extending through the beam and adapted to receive through bolts or mounting pins. Paired members I4 extend outwardly from the ends of beam I0 on opposite sides of the center thereof, and are each provided With a mounting point I6 similar to mounting point I2. Members I4, together With beam lil form a substantially U-shaped composite member, the members Ill being at right angles to beam ID; In the application of this mounting, mounting point I2 may be held fixed and the device to be protected suspended from mounting points it, or the converse arrangement in which mounting points I6 are xed and the device is suspended from mounting point I2 may be used. The operation of the mounting is the same for either of the arrangements just mentioned.

For Ian understanding of the operation of the mounting, it is convenient to assign a set of orthogonal reference axes (Fig.3) X-X, Y-Y, and Z-Z, in respect to which disturbing forces and translations ofthe protected device may be considered.` For convenience, the X-X axis (Fig. 3) Will be referred to as the longitudinal axis, the Y-Y axis as the transverse axis, and the Z-Z axis as the vertical axis. For the present, it will be assumed that the shock mounting is used with mounting point I2 fixed and that the protected device is suspended from mounting points I6.

Disturbing forces in the longitudinal direction X-X tend to cause translations of mounting points I6 in respect to mounting point I2, stressing rubber members I i in shear. In addition, such forces tend also to stress the portions of beam II) lying between mounting point I2 and members I4 in shear. The advantages of shearstressed rubber are, therefore, realized in protecting against vibration due to forces in the longitudinal direction.

Forces in the transverse direction Y-Y tend to cause translation of mounting points I6 in respect to beam I0. As a result each of members I4 is stressed in shear, providing for transverse disturbing forces.

Disturbing forces in the vertical direction Z-Z tend to translate the ends of beam I0 in respect to the center thereof, again loading the beam in shear. Since all disturbing forces may be resolved in the three orthogonal directions .porting an instrument tegral therewith body Yand legs thus protected, it will appear 'that good Vibration isolation` is provided irrespective of the directional distribution of the disturbing forces.

The exact form of beam land members I4, as Well as their cross sections, may be varied considerably to impart varying degrees of softness to the mounting, it being desirable in some cases to provide for greater protection in one or more of the three chosen directions.

One embodiment of the invention providing for somewhat greater protection in the transverse and vertical directions than in the longitudinal direction is illustrated in Fig. 2. In this mounting a beam 18 and paired members 20 are molded as one piece, thus forming a generally U-shaped composite member, mounting points 22 and 24 being positioned substantially as in the mounting shown in Fig. 1. Beam I8 is reinforced at its center by an additional amount of rubber, while the section at the point at which members 2i! join the beamis considerablyreduced, the entire structure being or" uniform thickness in the longitudinal direction. It Will be recognized that this structure is softer-that is, requires less force to produce a unit deflection-fin the transverse and vertical directions than in the longitudinal direction. Other variations inthe shapeof the beam and the outwardly extending members result in shock mountings having other characteristics, all of these mountings, however, providing for enhanced vibration isolation through the use of shear-loaded rubber in each ofk three chosen directions.

`We claim:

1. A vibration dampening .element for supporting an instrument on a panel comprising a U-shaped member consisting of arbody portion vand a pair of oppositely disposed legs attached .tion oi which is provided with a through hole substantially at the center thereof, and the legs of Which are provided With through holes near their ends, said throughA holes being parallel to each other and `ruiming transversely orv the member. 1 2. A vibration dampening element for supon a panel comprising a U-shaped member consisting of a body portion and apair of oppositely disposed leg portions inbeing of `substantially uniform cross-section and being composed o a non-metallic resilient unrestrained material, thefbody Y Vportion of which is provided with a, through hole substantially at the center thereof and the legs of which arel provided with through holes displaced laterally of said first named through hole near the ends o. the legs, said through holes beand at right angles thereto, said l portion ycent their free '4 ing parallel to each other and running transversely of the member.

3. A vibration dampening element for supporting an instrument on a panel comprising a substantially U-shaped member consisting of a body portion and a pair of leg portions at opposite ends of the body portions and substantially at right angles thereto, said member being of uniform cross-section and being composed of a nonmetallic resilient homogeneous material, the body of which is provided With a through hole substantially at the center thereof, and the legs of which are provided with through holes adjaends, the center line of said through holes being parallel to each other and normal to the plane in which said body and legs lie.

4. A vibration dampening element for supporting an instrument on a panel comprising a substantially yoke shaped member consisting of a thickened body portion and a pair of head portions of substantially the same diameter as the thickest'part of the body portion, said head portions being joined to the body portions by reduced neck portions, said member being of uniform thickness transverseiy thereof and being composed oi a non-metallic resilient homogeneous material, the body portion of which is provided with a through hole substantially at the center thereof in the thickest part thereof, and the head portion being provided with through holes substantially centrally thereof, the center lines oi' said through holes being parallel to each other and extending transversely of the member.

5. A vibration. dampening element for supporting an instrument on a panel comprising a member consisting of an elongated body and a pair of legs attached to opposite ends of the body, said member being composed of a non-metallic resilient material, the body of which is provided with a through hole substantially at the center thereof, and the legs of which are provided with through holes near their free ends, said through holes being parallel to each other and extending transversely of the member.

RALPH F. NORRIS. ROBERT D. AVERY.

References Cited in the le of this patent UNTED STATES PATENTS Number Name Date 1,410,765 Leas et al Mar. 28, 1922 1,420,082 Dowd June 20, 1922 2,037,032 Lord Apr. 14, 1936 2,269,245 Blessing Jan. 6, 1942 2.322,193 Kaemmerling June 15, 1943 

